The present invention generally relates to touch-sensitive devices and, more particularly, to methods of and systems for identifying at least one object on a touch-sensitive device.
Electronic products may generally be equipped with at least an input device to interact with users. Input devices, such as keyboards, mice, trackballs, touch pads, keypads and touch screens, are nowadays used as interfaces between users and electronic products. Examples of such electronic products include personal computers, laptops, mobile phones and personal digital assistances (PDAs).
Input devices which adopt touch-sensitive technology may be called touch-sensitive devices. Touch-sensitive devices, for example, touch pads and touch screens, may employ a matrix of row and column electrodes and detect variations in capacitance between row and column electrodes with respect to virtual ground. FIGS. 1A and 1B are schematic diagrams of column and row electrodes arranged within a touch-sensitive device 10 for capacitance detection. Referring to FIG. 1A, the touch-sensitive device 10 may include in a first layer thereof a number of column electrodes 11 having extensions 110 arranged in a pattern to detect capacitive variation when a finger moves along a direction “X” as shown by an arrowhead. Moreover, referring to FIG. 1B, the touch-sensitive device 10 may include in a second layer thereof a number of row electrodes 12 having extensions 120 arranged in a pattern to detect capacitive variation when a finger moves along a direction “Y” as shown by another arrowhead. The first layer shown in FIG. 1A may be disposed over the second layer shown in FIG. 1B (and vice versa) so as to form a matrix of column and row electrodes capable of detecting capacitive variations along both the “X” and “Y” directions.
FIG. 2 is a schematic diagram illustrating a method of recognizing a single finger on a touch-sensitive device such as the touch-sensitive device 10 described and illustrated with reference to FIGS. 1A and 1B. Referring to FIG. 2, a curve 2 may represent count values detected on each column electrode or trace of the touch-sensitive device, wherein each of the count values may be a digital value converted from an analog capacitance value. To recognize whether a finger contacts the touch-sensitive device, the peak “A” of the curve 2, which may have a count value “c1,” may be identified. Moreover, a point “B,” which may represent a trace “t1” on which a first valid count value may be detected, and a point “C,” which may represent a trace “t2” on which a last valid count value may be detected, may also be identified. Parameters “c1,” “t1” and “t2” may then be used to determine whether the curve 2 represents a finger by the following formulas:c1>Thresholdcv  (1)(t2−t1)>Thresholdtn  (2)
where Thresholdcv is a predetermined count value, for example, fifteen (ADC value, arbitrary unit), and Thresholdtn is a predetermined number of traces, for example, two traces. Hence, if the curve 2 satisfies the above formulae (1) and (2) in the current example, namely c1>15 (ADC value) and (t2−t1)>2 (traces), it may be identified that a finger represented by the curve 2 contacts the touch-sensitive device.
Nevertheless, with the advancement in electronic products, touch-sensitive devices have been required to allow multiple-finger operation in addition to single-finger operation. During the multiple-finger operation, it may be possible that two or more fingers may simultaneously press the column and row electrodes of the touch-sensitive device, resulting in a curve shape more complicated than the curve 2 in FIG. 2. Consequently, the above-mentioned formulae (1) and (2) may be inadequate for multiple-finger recognition.